Executive&#39;s and secretary&#39;s trunk connective intercommunication and signal system



April 17, 1951 R. F. STEHLJK; 2,549,719

EXECUTIVES AND SECRETARYS TRUNK CONNECTIVE INTERCOMMUNICATION AND SIGNAL SYSTEM Filed Sept. 12, 1947 4 Sheets-Sheet 1 FIG: I

INVENTO RUDG.PH F. STEHLIK ATTORNEY R. F. STEHLIK EXECUTIVES AND SECRETARYS TRUNK CONNECTIVE April 17, 1951 INTERCOMMUNICATION AND SIGNAL SYSTEM 4 Sheets-Sheet 2 Filed Sept. 12, 1947 zsa RUDOLPH F. STE HLIK ATTORNEY Aprll 17, 1951 R. F. STEHLIK 2,549,719

EXECUTIVES AND SECRETARYS TRUNK CONNECTIVE INTERCOMMUNICATION AND SIGNAL SYSTEM Filed Sept. 12, 1947 4 Sheets-Sheet 3 LINE 3 RUDOLPH F. STEHLIK ATTORNEY LINE 2 FIG-.3

LINE l April 17, 1951 R. F. STEHLIK EXECUTIVE'S AND SECRETARYS TRUNK CONNECTIVE INTERCOMMUNICATION AND SIGNAL SYSTEM 4 Sheets-Sheet 4 Filed Sept. 12, 1947 INVENTOR. RUDOLPH F. STEHLIK 6% ATTORNEY Patented Apr. 17, 1951 EXECUTIVES AND SECRETARYS TRUNK CONN ECTIVE INTERCOMMUNICATION AND SIGNAL SYSTEM Rudolph Frank Stehlik, Antwerp, Belgium, as-

signor to Automatic Electric Laboratories, Inc Chicago, Ill., a corporation of. Delaware i Application September 12, 1947, Serial No. 773,609

17 Claims. 1

The present invention relates in general to telephone systems and in particular to inter-i communicating systems which enable a local connection between an executive and his secretary and connections between either of these two stations and the local exchange.

' The invention is simple and compact in design yet entails a comprehensive system of signalling which enables both the executive and his secretary to tell at a glance the condititon of all of the lines available to them.

{One of the objects of the invention is the provision of improved circuit means for enabling an executive to talk over one trunk'line 'while holding a call on another trunk line or to talk to his secretary over a local connection while holding calls on either or both of the trunk lines.

Another object of the invention is an improved arrangement whereby the secretary is out ch from a trunk line over which the executive has established a connection.

A feature of the invention is the provision of both audible and visual signalling means which are operated in conjunction at different intervals toindicate either a calling line, a waiting line,

or a busy line.

Other objects and features of the invention will become apparent upon a further persual of the specification taken in conjunction with the accompanying drawings which disclose the invention when arranged as shown in Figure 5 with adjoining lines abutting.

Figures 1 and 2 show control relays and circuits associated with the trunk lines and the two substations. Figure 3 shows three trunk lines, line 3 being a private trunk line to the secretary. Figure 4 shows the substation equipment of the executive represented by B and his secretary represented by A. The substation equipment is comprised of a telephone transmitter T and receiver R, dial mechanism D, hook switch (or cradle switch) S1 and S2, lamps 4I-44, 5i54, and buzzers 48, 50. The invention anticipates the use of a substation telephone of the type disclosed in copending application Serial Number 773,110 filed September 10, 1947, now abandoned, having a five position rotary switch with lamps spaced around the arc described by the pointer knob of the rotary switch, each lamp corresponding to a particular position of said switch. It will be understood that the invention is not limited to the use of such a telephone but may 'be used with any conventional type of telephone I providing it has .a three spring hook o cradle switch. The five position control switch and associated lamps may be mounted in an operate unit or indeed the switch may be replaced by any kind of suitable switching means such as, for example, individual keys.

In order to better understand the invention, I will now explain the operation of the invention during a series of events as follows:

The secretary answers a call coming in over line #I and informs the executive over the intercom connection that the call is for him. The executive answers the call over line I and during the conversation discovers that he needs certain information from another outside party. The executive then dials out over line 2 and attains the desired informatiton, all the while holding his original connection. The executive then completes his conversation over line I and releases both connections simultaneously.

Referring now to the drawings, the call coming in over line #I, conductors I83, I84, operates,

through contacts 282, H9, conductor I3 of cable I to secretarys lamp 4| and battery. Buzzer 48 and lamp 4| operate every time relay 280 operates in response to the receipt of ringing current over the calling line. The secretary responds to these signals by lifting he telephone handset and moving her switch K1 to the position corresponding to lamp 4| thereby closing contacts 45. In lifting her telephone handset, the secretary operates the cradle switch S1. thus closing contacts 4IU4I2 and extending ground through contacts M2, 45, conductor I2 of cable I, contacts 366, 338, I61, and the winding of relay 220 to battery. Relay 220 operates and. opens a pulsing circuit to the secretarys lamp 43 at contacts 225, opens a locking circuit for relay.

240 at contacts 224, and extends ground through contacts 223 and winding of relay 398 to battery. Relay 220 also. connects the ground from con-. tacts. 4I-I1, through conductor CI of cable I, and contacts 221 to conductor I to thus busy line I. Relay 300 bridges the secretarys phone across the calling line at contacts 302 and 304, opens a bridging circuit at contacts 305, extends its operating ground to the upper winding of relay 2I0 at contacts 396, and opens energizing circuits for relays 36H, I69, and 238 at contacts 381, 388, and

' 309 respectively. Relay 2H1 prepares a line holding circuit at contacts 2! l, prepares a circuit to relay I20 at contacts 2 I2, prepares a new energizing circuit for secretarys lamp 4! at contacts 2 I4, energizes lamp 5| from ground at contacts 2I5 through contacts 259, conductor 24 of cable 2, and lamp 5| to battery, and locks up over its lower Winding from battery, lower winding of relay 2 I0, contacts 2 I3, 225, conductor II of cable I, and contacts M to ground. It will be noticed that the lamp i, corresponding to line I, is now energized by a steady current indicating the busy condition of line I. It will also be realized that the secretary in answering the call, causes ringing current to be disconnected from the calling line in a well known manner thus causing relay 280 to remain deenergized and deenergizing her lamp 4I and buzzer 40.

The secretary finds that the'call is for the executive and consequently moves her switch K1 to the intercom position thereby opening contacts 45 and closing contacts 46. The opening of contacts 45 opens the energizing circuit of relay 220 which restores and prepares a pulsing circuit to secretarys lamp 41 at contacts 225, prepares a locking circuit for relay 240 at contacts 224, opens the energizing circuit of relay 300 at contacts 223, and completes an energizing circuit for relay I20 at contacts 222. Relay 300 restores and places a holding bridge including contacts 2!! and resistance R1 across line I at contacts 305, and disconnects secretarys phone from line I at contacts 302, and 304. Relay I20 operates from ground at contacts 222, through contacts 3I1, 2I2, I32, and winding of relay I20 to battery. Slow to release relay I20 and I30 form a pulsing circuit as follows: relay I20 operates relay I30 at contacts I2I and relay I30 opens the energizing circuit of relay i20 at contacts I32. Relay I20 restores after a slight delay and opens the energizing circuit or relay I30 at contacts I2I. Relay I30 restores after a slight delay and re-energizes relay I20 at contacts I32 whereupon the cycle of operation keeps repeating itself. Everytime relay I30 operates it connects ground at contacts I34 through contacts 225, 2I4, 251, conductor I3 of cable I, and secretarys lamp 4| to battery. Lamp 4I flashes at a rate dependant upon the natural cyclic period of operation of relays I20 and I 30 thus indicating that line I is in a waiting condition. Relay I60 operates from ground at contacts 4I2, through contacts 46, conductor I4 of cable I, contacts 361, 338, 308, and Winding of relay I60 to battery. Rela I60 completes an energizing circuit for relay I at contacts I6I and I62, completes an energizing circuit for lamp 52 at contacts I63, completes an energizing circuit for buzzer 50 at contacts I65, and opens the circuits to relays 360, 220, and 230 at contacts I66, I 61, and I66 respectively. Everytime relay I30 operates the lamp 52 flashes over the circuit from ground at contacts I3I, through contacts I4I, I63, conductor 26 of cable 2, and lamp 52 to battery. The buzzer also operates everytime relay I30 operates, from battery through the lower winding of relay I10, contacts II2, I33, I45, I65, conductor 2I of cable 2 and buzzer 50 to ground. The executive now has an audible signal that someone is calling and a visual signal that the calling party is his secretary calling over the intercom as indicated by the flashing of lamp 52. It will be noted that the upper and middle windings of relay I10 are bridged by the secretarys substation line (conductors L1 and +L1) through contacts IGI and I62 hence rela I10 operates. Relay 10 furnishes an auxiliary operating ground at contacts ill for the pulsing relays I and I 30.

The executive responds to his secretarys call by moving his switch K2 to the position corresponding to the lamp 52 thereby closing contacts 56, and by lifting his telephone handset thereby operating the cradle switch S2 and closing contacts 42I, 422, and 423. Relay I50 now operates from ground at contacts 423 through contacts 56, conductor of cable 2, winding of relay I50, contacts 3I0, and 349 to battery. Relay I50 bridges the executives speaking leads +L2 and L2 across the secretarys speaking leads +L1 and L1 at contacts I 5I and I52, completes a circuit to relay I at contacts I54, and opens the circuits to relays 260 and 210 at contacts I56 and I51 respectively. Relay I40 operates from ground at contacts I54 through contacts I64, and winding of relay I40 to battery. Relay I40 opens an energizing circuit to secretarys lamp 42 at contacts MI and opens the energizin circuit of lamp 52 at contacts I4I thus extinguishing lamp 52, locks up to ground from contacts I H through contacts I43, opens a circuit to the secretarys buzzer 40 at contacts I44, opens the energizing circuit to buzzer 50 at contacts I45 thus silencing buzzer 50. The executive is now connected to his secretary over the local intercom line, talking battery for the connection being had through the upper windings of relay I10. At this time secretarys lamp M is flashing and bosss lamp 5| is steadly energized.

The executive, after talking with his secretary, desires to talk to the calling party on line I hence he moves his switch K2 to the position corresponding to lamp 5| thereby opening contacts 56 and closing contacts 55. The opening of contacts 56 opens the energizing circuit of relay I thereby causing it to restore. In restoring, relay I50 removes the executive's speaking leads from across the secretarys speaking leads at contacts I5I and I52, opens the original energizing circuit of relay I40 at contacts I54, opens a point in a circuit to secretarys buzzer 46 at contacts I55, and closes points in the energizing circuits of relays 210 and 260 at contacts I56 and I51 respectively. If the secretary hangs up now, relays I60 and I10 will restore but We will assume, for the sake of illustration, that the secretary does not hang up immediately but instead, tries to listen in on the connection between the executive and the calling party on line I. lhe closing of contacts 55 causes relay 265 to operate after relay 50 releases from ground at contacts 423 through contacts 55, conductor 23 of cable 2, contacts I51, 348, and winding of relay 260 to battery. Relay 260 completes a circuit to relay 3 I 0 at contacts 264, opens a circuit to the lamp 5I at contacts 265, and connects ground from conductor C2 to conductor I at contacts 262 to busy line I. Relay 3I0 connects the calling line (conductors I83 and I84) to the executives speaking leads L2 and +112 at contacts 3I2 and 3 l 1, opens a point in a holding circuit at contacts 3| I opens a point in another holding circuit at contacts 3I5, extends its operating ground to relay 250 at contacts 3I6, opens the energizing circuit of relay I20 at contacts 3I1, and opens further points in energizing circuits for relays 210 and I50 at contacts 3I8 and iii!) respectively. Relays E20 and I30 restore thus extinguishing the secretarys lamp M at contacts 134. Relay 250 operates from ground at contacts 234 through contacts 3I6, and upper winding of relay 250 to battery. Relay 250 closes a point in a new hold-.

, ing circuit at contacts 252, closes a point in an 255 to release. relay 2H], completes an energizing circuit for secretarys lamp 4I at contacts 255; prepares an energizing circuit for lamp 5I at contacts 258, and locks up over its lower'winding from ground at contacts 42I, through conductor 22 of cable 2, contacts 254, and lower winding of relay 25!] to battery. The secretarys lamp ii is now energized by a continuous current from ground at contacts I02 through contacts 255. conductor I3 of cable I, and lamp 4| to battery.

C3 completes a circuitfor the pulsing. relays I20 and I30 at contacts 213, and completes a pulsing circuit to lamp 5I at contacts 265 which extends This steady light indicates to the secretary the busy condition of line I.

Suppose now that the secretary tries to listen in on the conversation in which case she would move her switch K1 to the position corresponding to lamp 4I thereby closing contacts 45. In closing contacts 45, relays 225, 350, and 2H} will operate in a manner similar to their operation when the secretary originally answered the in coming call on line I. Ordinarily the secretary s speaking leads L1 and +L1 would be connected to conductors I33 and I 84 of line I at contacts 352 and 334 but due to the operated condition of relay 3ID, contacts 352 and 364 are ineiiective thus preventing the secretary from listening in on the connection between the boss and line I. Even if the executive should move his switchK-i to a new position resulting in the restoring of relay 3H}, (as will be explained hereinafter) the holding bridge including resistance R1, contacts 252, and 385 which will bridge line I will prevent the secretary from talking in on line I because the holding bridge is connected across the line conductors of line I and contacts 382 and 594.

Let us go back to the time when the secretary has called the executive on the intercom line and he has answered her. At this time relays 2I0, 160, I50, I10, I48, and pulsing relays E and I are operated and secretarys lamp 4| is flashing everytime relay I35 operates. The holding bridge including contacts 355, ill I, and resistance R1 is holding the calling party on line I. When the executive moves his switch to the position' corresponding to line I, relay I50 restores and relays 285, (H5, and 250 operate as has been described. It will be realized that the aforementioned holding bridge is being maintained by relay 2 I ll which is locked up over its lower winding to ground through the secretarys hook switch. If she should hang up before the eXecutive operates relay 3m to bridge his subset across line I, the connection would be released hence she waits until she gets a steady indication of her lamp 4| before hanging up thus assuring the maintenance of the holding bridge across line I until relay 3H3 has operated to substitute the executives phone for this bridge. When the secretary hangs up, the cradle switch S1 opens contacts 4H], 4H, and 4I2 thereby opening the energizing circuit for relay I55 which restores contacts I5! and IE2 open the energizing circuit of relay I'll] which restores and at contacts II I, opens the locking circuit for relay I which in turn restores.

Returning now to the condition where the executive is in conversation with the calling party during the course of which he discovers thathe needs some information from another party which he desires to obtain without releasing the calling party on line I. The executive now moves his switch K2 to the position corresponding to line 2 thereby opening contacts 55 and closing contacts 5'I. The opening of contacts 55 opens the energizing circuit of relay 260 which restores and from ground at contacts I35 (everytime relay I39 operates) through contacts 265, 258, conductor 24.of cable 2, and lamp 5I to battery. The flashing lamp 5| indicates, as before, the waiting condition of .line I.' Relay 255 also opens the energizing circuit of relay 3Ifi at contacts 254 thus causing relay 3H3 to restore and connect a holding bridge including contacts 3I5, 252, and resistance R1 across conductors I33 and I84, and disconnects the speaking leads -L2 and +L2 from across line I at contacts 3I2 and 3I4. Relay 270 now operates from ground at contacts 423, through contacts 51, conductor Z'I of cable 2, contacts I5 6, 3I8, and winding of relay 210 to battery. Relay 2T0 connects ground to the control conductor 285 of line 2 at contacts 212 as follows; ground at contacts 422 of cradle switch S2, conductor C2 of cable 2 and contacts 212 to conductor 285. Relay 210 also completes an obvious circuit for relay 350 at contacts 274, and opens a circuit to lamp 53 at contacts 215. Relay 340 operates and connects the executives speaking leads L2 and +112 to conductor 283 and 284 of line 2 at contacts 342 and 344. This looping of line 2 by the executives substation starts the operation of well known succeeding switches to permit the extension Of a call from the instant station to any other subscriber local or otherwise. The ground applied to conductor 285 by relay 21D, busies line 2 to incoming calls. Relay 340 also opens a'point in a, holding bridge at contacts. 345, extends its operating ground to relay 240 at contacts 346, opens a circuit to relay 260 at contacts 348, and opens a circuit to relay I at contacts 349. Relay 245 operates from ground at contacts 274 through contacts- 346, and upper winding of relay 240 to battery. Relay 240 prepares a holding bridge circuit for line 2 at contacts 242, prepares an auxiliary operating circuit for pulsing relays I 20 and I30, opens the locking circuit for relay 250 at contacts 245, completes a circuit for secretarys lamp 43 at contacts 246, and prepares a circuit for lamp 53 at contacts 248. The secretarys lamp 43 is now steadily energized over the circuit from ground at contacts I02 through contacts 246, conductor ll of cable I, and lamp 43 thus indicating the busy condition of line 2. The executive may now operate his dial mechanism D2 to call the desired party as soon as he receives dial tone from the subsequent switch train.

Upon completing his conversation with the called party, the executive desires to impart the information he has received from the called party on line 2 to the calling party on line I. The executive consequently, without replacing his telephone handset, moves his switch K2 to the position corresponding to line I thereby opening contacts 51 and closing contacts 55. Contacts 51 open the energizing circuit of relay 210 which restores causing relay 340 to restore at contacts 214 and completing a pulsing circuit to lamp-53 at contacts 215. Relay 340 disconnects the speaking leads L2 and +L2 from across line 2 at contacts 342 and 344 and connects a holding bridge across line 2 which includes resistance R2, contacts 242, and 345. Lamp 53 is energized from ground at contacts I35 (everytime rela i3I) operates) through contacts 215, 248, conductor 28 of cable 2, and lamp 53 to battery. The closing of contacts 55 completes an energizing circuit for relay 260 from ground at contacts 423 through contacts 55, conductor 23 of cable 2,- contacts I51, 348, and winding of relay 2-60 to battery. Relays 260, and 3 I operate in the same manner as they did when the executive first answered the call on line I only in this case relay 250 is already locked energized from ground supplied from contacts 42I of cradle switch S2. The executives speaking leads L2 and +Lz are again connected to conductors I33 and I 84 of line I at contacts 3I2 and 3| 4 and the holding bridge for line I has been opened at contacts 3I5 by the operation of relay 3I0. It will be noted that the pulsing circuit to lamp 5| is opened at contacts 265 by the operation of relay 260. Briefly, at this time, we have secretarys lamps M and 43 steadily energized from ground at contacts I02, lamp 53 is flashing everytime relay I30 operates, and relays 260, 3I0, 250, 240, and pulsing relays I20 and I30 are operated.

Upon the completion of his conversation with the calling party on line I, the executive will release both lines I and 2 by replacing his telephone handset thereby operating his cradle switch S2 to open contacts 42 I, 422, and 423. The opening of contacts 42I opens the locking circuit for relays 240 and 250 which now restore. 'Relay 250 opens the energizing circuit for lamp M at contacts 256. Relay 240 opens the ener gizing circuit for lamp 43 at contacts 246, and for lamp 53 at contacts 240. Relay 243 also opens the energizing circuit for pulsing relays I20 and I30 at contacts 243. The opening of contacts 423 opens the energizing circuit of re lay 2'60 thereby causing it to restore. Relay 2% opens the energizing circuit of relay 310 at contacts 264, causing relay 3I0 to restore and disconnect the executives speaking leads from across line at contacts 3I2 and 3I4. The closing of contacts 3I5 are ineffective, in this case, to place the holding bridge across line I, because of the open condition of contacts 252'. The entire system is now at normal ready to receive or extend any new calls.

It will be realized that a call coming in on line 2 would be handled in a similar manner to the way in which the call coming in on line I was handled as has just been described. In the case of line 2 calling, relay 320 would operate on every ring cycle to signal the secretary by operating her lamp 43 and buzzer 40. secretary, in answering the call, would operate relays 230, 330, and 200 which is analogous to the operation of relays 220, 300, and 2I0 as has been previously explained. The transfer of the call to the executive is the same as for the first case as is the final release of the connection.

It will be further realized that either the executive or his secretary may call each other and converse over the intercom connection irrespective of the condition of the trunk lines. If the executive desires to call his secretary he lifts his telephone handset and moves switch K2 to the intercom position thereby closing contacts 42I, 422, 423, and 56. Relay I50 operates from ground at contacts 423 through contacts 56, conductor 25 of cable 2, winding of relay I50, contacts 3I9 and 349 to battery. Relay I50 bridges the executive's substation across the upper and middle windings of relay I at contacts I5I and I52, prepares a circuit to secretarys lamp 42 at contact I53, prepares an energizing circuit for relay I40 at contacts I54, and prepares a circuit for secretarys buzzer 46 at contacts I55. Relay I10 operates over the executives substation loop in an obvious manner, and completes The an obvious start circuit for the pulsing relays I20 and I30 at contacts I1I. Everytime relay I30 operates it completes an energizing circuit, for lamp 42 from ground at contacts I3I, through contacts I4I, I53, conductor I5 of cable I and lamp 42 to battery. Relay I30 also completes a circuit for buzzer 40 at contacts I33. This circuit may be traced from battery through the lower winding of relay I10, contacts H2, I33, I44, I55, conductor I 0' of cable I, and buzzer 40 to ground. Everytime buzzer 40 operates the executive hears a buzzer tone through the medium of the inductive coupling furnished by the windings of relay I10. This tone indicates that his secretary is at her desk. The absence of the tone would tell him that the secretary has operated her away from desk switch as will be hereinafter explained. The secretary responds to these signals by lifting her telephone handset and moving switch K1 to the position corresponding to lamp 42 thereby closing contacts M0, 4, 4I2, and 46. Relay I now operates from ground at contacts 4I2 through contacts 46, conductor I4 of cable I, contacts 361, 339, 308, and winding of relay I60 to battery. Relay I60 connects the secretarys speaking leads L1 and +L1 to the SIXBClltlVES speaking leads L2 and +L2 at contacts I6I and I62, and completes an obvious energizing circuit for relay I40 at contacts I64. Relay I40 opens the start circuit for pulsing relays I20 and I30 at contacts I42, locks up to ground at contacts I'II through contacts I43, and opens the energizing circuits for lamp 42 and buzzer 40 at contacts MI and I44 respectively. The conversation between executive and secretary may now take place, talking battery being had through the upper and middle windings of relay I10. The intercom connection is released in an obvious manner when both parties have hung up or moved their control switches to different positions.

Consider now the operation of the system when a call comes in on line 3 which is a private line tothe secretary. Relay 350 operates on every ring cycle in a well known manner thereby connecting ground at contacts 352 through contacts I I9, conductor I9 of cable I, and lamp 49 to battery. Relay 350 also completes a circuit for secretarys buzzer 40 at contacts 35I as follows: from battery at resistance 90, (Figure 1) through conductor I93, contacts 35I, conductor I9I, contacts H5, H4, conductor I0 of cable I, and buzzer 40 to ground. The secretary responds to these signals by moving her switch K1 to the position corresponding to line 3 thereby closing contacts 48 and by removing her telephone handset thereby operating cradle switch S1 to close contacts 4I0, 4| I, and 4I2. Thus ground from contacts M2 is extended to relay 360 through contacts 48, conductor I8 of cable I, contacts 331, 301, I66, and winding of relay 360 to battery. Relay 360 operates thus connecting the secretarys speaking leads L1 and +L1 to conductors 383 and 384 of line 3 at contacts 363 and 365 and busying line 3 to other incoming calls by grounding control conductor 355 at contacts 36I as follows; from ground at contacts 4H through conductor C1 of cable I and contacts 36I to conductor 385. Relay 360 also opens the energizing circuits for relays 226, I60, and 233 at contacts 356, 361, and 368 respectively. While no holding bridge is shown for line 3, it is to be understood that such a bridge may be easily provided in a manner Silllilar to the holding bridges shown for lines I and 2. The connection will be released when the secre- U tary replaces here telephone handset thereby opening the energizing circuit for relay 36!] at contacts M2 thus returning the system to normal. The secretary may call out on her private line by operating switch K1 in the same manner as for answering a call on line 3, in which case relay SEE-bridges the secretarys substation across secretary has moved her switch to the away from'desk position and a call comes in over line 2. The closing of contacts 19 extends ground through conductor 28 of cable I and the winding of relay I t to battery. Relay lilll opens an ener gizing circuit for secretarys lamps 4| and 33 at contacts Hi2 and completes an obvious energizing'circuit-for relay! ill at contacts It]. Relay i-lii transfers the operating battery for the buzzers from the lower winding of relay We to the circuit including resistance 90, transfers an operating circuit for secretarys buzzer to the executives buzzer at contacts H3, and H4, opens the circuit to the secretarys buzzer at contacts H5, transfers the operating circuits for secretarys lamps H and G3 to the eXecutives lamps 5| and 53 at contacts 5 is and H8, and opens the circuit to secretarys lamp Mi at contacts H9. Relay 32% operates on every ring cycle over the calling line in a now familiar manner, and connects ground at contacts 322 through contacts H6, conductor 28 of cable 2, and lamp 53 to battery. Relay 320 also completes a circuit to the buzzer 50 at contactsBZi as follows; from battery at resistance 9t (Figure 1) through conductor I93, contacts 32f, conductor E92, contacts I53, conductor 2! of cable 2, andbuzzer 5? to ground. Buzzer 5i} and lamp 53' thus operate everytime relay 32R operates thereby indicating to the executive the calling condition of line 2.

; tercom position thereby closing contacts 42 i, 322,

123, and 5% Relay 156 now operates from battery atcontact-s 349 (Figure 3) through contacts 319,

winding of relay 556, conductorZE of cable 2,

contacts 55 and 23 to ground. Relay lfii} bridges the executivesspeaking leads L2 and +L2 across the upper and middle windings of relay I'lil at contacts I54 and 152 thereby causing relay Iii; to operate. Relay l'Hl completes an obvione start circuit for the pulsing relays 12K; and [Elli-Eat contacts I'H. Everytime relay. Hit operates, it completes a circuit for the secretarys buzzer at contacts I 33; and IE5. This circuit may contacts lll, I33, [4:3, E55, conductor iii of cable '1 andbuzzertfi to ground. interrupter relay I39 at. contacts. 13! completes a circuit by way of contacts [4t and IE3, conductor [5 of cable I,

The executive answers the in call by removing his handset and by moving lay H0, everytime buzzer ii! operates.

iii and lamplZ to battery to flash lamp 42. .Ordinarily, the battery for operating the secretarys buzzer when the executive is calling over the intercom connection, comes from the lower winding of relay I'll! through contacts i 52 thus giving the executive a tone indication, through the in-' ductive coupling furnished by the winding of re In the present case, however, the operating battery for buzzer as is fed through resistance 95 and contacts iii hence the executive will not receive a tone indication and he will therefore know that the secretary has operated her away from desk switch.

A call coming in over the secretarys private line, line 3, will not operate any signaling devices at either substation due tothe open position. of contacts H9 and H5. 7

For the sake of simplicity I have not shown any utility for executives lamp E i and switch contacts 53 and 59. It is to be understood that these devices may be used in a number of ways. instance lamp 54 and contacts 58 might be used for a private line to the executive in the same way as lamp 44 and contacts Q8 are used for the'secretarys private line. Contacts 59 might be used to signal to the secretary that the executive does not wish to be disturbed or for summoning a subordinate to the executives office, etc.

Certain of the relays in this invention such as, for example, relays 260, 210, Slit, 3E5 etc., have been made slow to release by the addition of a copper slug around the armature end of the relay. It is a characteristic of this type of relay that it is also slightly slow to operate. The reason for these slugged relays is to prevent false signalling and false connections. Suppose that the executive is holding a callon line 2 while talking on line I. In this case relays 250, 3H and pulsing relays I28 and I30, among others, are operated. Now the executive switches over to connect with the waiting line 2. If he should pause momentarily at the intercom position, which lies between the line i and line 2 positions, relay 950 would operate to signal the secretary if it were not for the fact that relays 260 and m are slow to release and relay i513 cannot operate until relay 3H) releases because of contacts M9. 7 Relays 220, 230, 260, and 2H! are also slightly slow'to operate so that the very slight period that the contacts for operating these relays are closed during the normal turning of switch K2 to an other position will not be long enough to operate these relays. This feature is part of a general interlock system which prevents one person from operating two trunk connecting relays at one time. Take again, for instance, the case where the executive is holding a call on line 2 while talking on line [in which case trunk connect relay 3"] isoperated. Now when the executive desires to return to the party on line 2 he will 'be traced from battery at resistance 92 through move his switch K2 so as to operate relay 210 which in turn willoperate trunk connect relay 340. Relay 2112- however, cannot operate until trunk connect relay 3H] restores because of contacts 3E8. Thus we see that trunk connect relays 3 l8 and 346 cannot be operated at the same time for if they were the two lines 5 and 2 would be cross'connected. The same, of course, is true for the trunk connect relays controlled by the secretary, namely relays Silt, 330, and 36B. While there has been described what is at pres ent considered to be the preferred, embodiment of the invention, it will b'e'understood that various 7 modifications maybe made therein, and it is in- For 11 tended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:'

1. In a telephone system, a plurality of subscribers stations, a plurality of trunk lines common to said stations, visual signaling means in dividual to each of said trunk lines at each of said stations, means responsive to a calling one of said trunk lines for operating the signal means individual thereto at a particular rate and at only a particular one of said stations, and means operated at said particular station after the operation of said signaling means for causing the signaling means at another one of said stations which is also individual to said calling trunk to operate at a different rate.

2. In a telephone system, a first subscribers substation and a second subscribers substation, a plurality of trunk lines common to both of said substations, a plurality of signaling means at both of said substations each being individual to one of said trunk lines, means responsive to a call on one of said trunk lines for operating the signaling means individual thereto only at said first substation and means operated at said first substation for causing said first substation to be connected to said calling trunk line and for operating the signaling means individual to said calling trunk line at said second substation.

3. In a telephone system including first and second subscribers stations and a plurality of trunk lines common thereto, a plurality of visual signaling devices located at each of said stations, each of said signaling devices being associated with a particular one of said trunk lines, means for communicatively connecting said stations over a local connection, means responsive to a call on one of said trunk lines for operating the signal device associated therewith at a particular rate but only at said first station, means controlled from said first station for causing said first station to be connected to said calling trunk, other means controlled by said third means for causing the signal device at said second station associated with said calling trunk to operate at a different rate, and contact means for controlling said second means to restore said first operated signaling device when said third means is operated by the subscriber at said first station.

4. In a telephone system including first and second subscribers stations and a plurality of trunks common thereto, each of said stations being provided with a signaling device individual to each of said trunk lines, means operable from either of said stations for communicatively connecting said stations over a local connection, means responsive to a call on one of said trunk lines for operating the signal device associated therewith at one particular rate but only at said first station, means controlled from said first station for connecting said first station to said calling trunk line, means controlled by said third means for operating the signaling device at said second station individual to said calling trunk line at a different rate, means operative at said first station for operating said first operated signaling device at a still different rate, other means controlled from said second station for connecting said second station with said calling trunk line, and means for causing said first operated signaling device to operate at said different rate in response to the operation of said other means,

5. In a telephone system including first and second subscribers stations having a trunk line 12 common thereto, trunk line signaling means at each of said stations individual to said trunk line, said trunk line signaling means normally operated only at said first station responsive to an incoming calling condition of said trunk line, control means controlled from said first station for conditioning said system so that only the trunk line signaling means at said second station will operate responsive to an incoming calling condition of said trunk line, means for establishing a local connection between said stations over an interofiice line, audible signalling means at each of said stations individual to said interoffice line and means including a relay controlled from said second station for operating said audible signalling means at said first station, the operation of which is normally made audible to the subscriber at said second station through the inductive coupling of the windings of said relay but being made inaudible to the subscriber'at said second station when said control means is operated.

6. In a telephone system including a scoretarys substation and an executives substation, a plurality of trunk lines common to said sub,- stations, each of said substations being provided with a lamp individual to each of said trunk lines, a relay intermittently operated at a particular rate in response to a call on one of said trunk lines, the lamp individual to said calling trunk line only at said secretarys substation operating in response to each operation of said relay, a switch manually operated by the secretary to a particular position in response to the operation of said operated lamp, and a second relay operating in response to the operation of said switch to said particular position for causing the lamp at said executives substation individual to said calling trunk to operate at a rate difierent from the operating rate of said first operated lamp.

'7. In a telephone system including a secretarys substation and an executives substation, a plurality of trunk lines common to said substations, each of said substations being provided with a lamp individual to each of said trunk lines, a relay intermittently operated at a particular rate in response 'to a call on one of said trunk lines, only the lamp at said secretarys substation individual to said calling trunk line operating in response to each operation of said relay, a switch manually operated to a particular position in response to the operation of said operated lamp, two relays operating in response to the operation of said switch to said particular position for causing said secretarys substation to be connected to said calling trunk line, and a fourth relay operated in response to the operation of said switch to said particular position for causing the lamp at said executives substation individual to said calling trunk line to operate at a rate different from the operating rate of said a plurality of trunk lines common to said subtion for initiating a local connection between said substations, a relay connected to one of said trunk lines and intermittently operated at a particular rate in response to a call on said one of said trunk lines, means controlled by said relay apt 19, 719

' for operating; only thelamp atzsaid. secretary's substation individual to said, calling trunk-.iline inresponse to each operation-of said: relay, said switch'manually operatedlto. asecondlposition of said two relays, means for causing the lamps atsaid executives substation individual tosaid calling trunk line to operate ata rate v different from the operating rate. ofv said first; operated lampin response, to theoperationof saidjthird' relay, said two relays deenergized responsive; to the manual operation of said, switchirom saidsecond position to said first position-interrupter means, means for. operating; said: interrupter means in response to .the deenergizatiomofisaid. two'relays, and meanscontrollediby saidinten rupter means for causing said, first. operated lampsto operate at a stilldiflerent'rate;

9. Ina telephone system as. claimed inclaim 8 in' which said executives substation is: provided with a manually operable switch, operated to. a; particular position corresponding to the operation of said operated lamp; at said executives substation, a pair of relays, means'foropcrating said pair ofrelaysvin responseto the operation of said second'switch to said particular position, meanslfor. causing saidzexecutives substationto be connected to said calling trunk'line in responseto. the operation of said pair ofrelays, a further relay, means for operating said further relay in response to the operationfof ,said pair of relays, means for extinguishing said operated lamp atjsaidexecutives; substation in responseto the operationof said-further-relay, and means for: causing said firstoperatedlamp tooperate' at said diiferent rate in, responseto the operation of said further relay.-

10. In a telephone system including a secretarys substation and an executives substation,

a plurality of trunk lines common to said substations, a manually operableswitch at said secretarys-substation,.meansresponsive to the operation ofsaid'switch to a first,,position for initiating a local connection between said substations, two relays, meansfor operating said two relays responsive to the operation of said-.gswitch tota second position means for connectingsaid secretarys. substation to a particular one ofsaid trunk lines in response to the operation. of said two'relays, aholdingbridge circuit for saidparticular trunk line, a third relay, means for operating said third relay responsive to the operation of said two relays, means for preparing said holding bridge circuit for said particular trunk in response to the operation of said third relay, said two relays deenergized responsive to the operation of said switch from said second position to said first position, and means for completing said holding bridge circuit in response to the deenergization of said two relays.

11. In a telephone system as claimed in claim 10 in which said executives substation is provided with a manually operable switch, a pair of relays, means for operating said pair of relays responsive to the operation of said executive switch to a particular position, means for causing said executives substation to be connected to said particular trunk line in response to the 1'4 operation. ofgsaidpair'of relays; andzmeans COR? trolledbysaidipair of relays to; prevent said; sec;- retarys; substation from. reestablishing: a connection with said; particular trunk, line;

12.; In a; telephone system as claimedin claim 10, a manually operable switch: at said executives substatioma pair of relays,means-foroperating said pair of relays responsive to. thev operation; of saiclexecutiveswitch toa, particular position, means operated responsive to theoperation of said pair of relaysforcausing said executives substation tobe connected-1 to said particular.

trunk line, asiX-threlay, means for operating saidsixthrelay in response to thesoperationof said; pair: of relays,;means operated; responsive to; the operation of the sixth relay for preparing said; holding, bridge; circuitfor saidparticular trunk line, saidpair of, relays deenergized responsive; to the; operation of said executive;

switch to. a different position, and means: for

completing; said; holding bridge; circuit respon sive: to. the deen-ergization; of; saidv pair 1 of relays.

13. .Ina; telephone; system; a subscribers substation, a trunk line, a visual signal at said substation individual togsaid trunk line, signalling means. responsive to, anrincoming call received oversaidtrunkJine:for-flashingsaid signal at-a predetermined rate, answer means-responsive to the subscriber at'said substationanswering the trunk call for connecting said substation to said trunk line, contact means controlled byv the operation of said answer means; for controllingsaid signalling; means to. extinguish said. signal, an incomplete holding bridge for. said trunk; line, othermeans for enabling said subscriber to control saidzanswerr means to disconnectyhis substationfrom. said trunk line, further contact means operated to complete said holdingv bridge for-saidtrunk line in response to the operation of. said other means, flashing means operated to flash. said signal at a different predetermined rate-in response to the operation. of saidother means, additional means including a second subscribersi line for connecting said second subscribers line'with said trunk line, contact .means operated by said additional means for removing said'holding bridge, and contact means responsive; to theoperation of said: additional means for, maintaining said, signa-l'illuminated.

14. Ina telephone-system, afirstsubscribers line, asecondsubscri-bers line, a.trunk, a first visual. signal individual tosaid trunk and individual tosaidfirst line, a secondvisual signal individual tosaid, trunkand individual tosaid second line, signalling means responsive to-an incoming callreceived over said trunk for flashingonly-sa'idfirst signalata predetermined rate, answer means responsive to the first subscriber answering said trunk call for connecting said first subscriber line to said trunk, contact means for controlling said signalling means to extinguish said first signal in response to the operation of said answer means, other contact means responsive to the operation of said answer means for steadily illuminating said second signal, an

incomplete holding bridge for said trunk line, additional means for enabling said first subscriber to control said answer means to disconnect said first line from said trunk, a circuit closed responsive to the operation of said additional means to complete said holding bridge, flashing means operated by said answer means and said additional means to flash said first signal at a differentpredetermined rate, means for signalling the second subscriber in response to the operation of said additional means, further means for enabling said second subscriber to connect with said trunk, means controlled by said further means to remove said holding bridge from said trunk, means operated by said further means to extinguish said second signal, and controlled by said further means to maintain said first signal illuminated.

15. In a telephone system, a subscribers line, a first and a second trunk, a first trunk relay individual to said first trunk for connecting said first trunk to said line, a second trunk relay individual to said second trunk for connecting said second trunk to said line, a first control relay for controlling the operation of said first trunk relay, a second control relay for controlling the operation of said second trunk relay, a circuit for energizing said first control relay including contacts on said second trunk relay and contacts individual to said trunk at said line, and a circuit for energizing said second control relay including contacts on said first trunk relay and contacts individual to said second trunk at said line.

16. In a telephone system, a subscriber substation, relay switching apparatus associated with said substation, an intercommunication line and a first and second trunk terminating in said apparatus, an intercom relay in said apparatus for connecting said line to said station, a first trunk relay in said apparatus for connecting said first trunk to said station, a second trunk relay in said apparatus for connecting said second trunk to said station, a circuit for energizing said intercom relay including contacts on said first and second trunk relays and contacts individual to said line at said substation; circuit; means for energizing said first trunk relay including contacts on said intercom relay, contacts on said second trunk relay and contacts individual to said first trunk at said substation;

and circuit means for energizing said second trunk relay including contacts on said intercom relay, contacts on said first trunk relay and contacts individual to said second trunk at said substation.

1'7. In a telephone system, first and second subscriber substations, relay switching apparatus associated with said substations, an intercommunication line and first and second trunks terminating in said apparatus, an intercom relay for each substation in said apparatus for interconnecting said substations over said line, a first trunk relay in said apparatus individual to said first substation and to said first trunk for connecting said first trunk to said first substation, a second trunk relay in said apparatus individual individual to said line; a circuit for energizing the second of said intercom relays including contacts on said third and fourth trunk relays and contacts at said second substation individual to said line; circuit means for energizing said first trunk relay including contacts on the first of said intercom relays, contacts on said second trunk relay, and contacts individual to said first trunk at said first substation; circuit means for energizing said second trunk relay including contacts on the first of said intercom relays, contacts on said first trunk relay, and contacts individual to said second trunk at said first station; circuit means for energizing said third trunk relay including contacts on the second of said intercom relays, contacts on said fourth trunk relay and contacts individual to said first trunk at said second substation; circuit means for energizing said fourth trunk relay including contacts on the second of said intercom relays, contacts on said third trunk relay and contacts individual to said second trunk at said second substation; contacts on said third trunk relay operated in response to the energization of said third trunk relay for disconnecting said first substation from said first trunk in case said first station is connected thereto, and contacts on said fourth trunk relay operated in response to the energization of said fourth trunk relay for disconnecting said first substation from said second trunk in case said first substation is connected thereto.

RUDOLPH FRANK STEHLIK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Beaumont Apr. 1'7, 1945 

